1. Field of the Invention
This invention relates to fossil-fuel fired steamers used in the preparation of foods. More particularly, this invention relates to a fossil fuel-fired boilerless steamer used in steaming foods such as potatoes and other vegetables.
2. Description of Prior Art
In some steamers being manufactured and in use today, steam is generated in a separate boiler and transported to the steamer. There are, however, steamers which generate steam directly in the steam chamber known as boilerless steamers.
Boilerless steamers are devices in which a steam chamber is disposed within a housing and water disposed in the lower portion of the steam chamber is heated to a temperature suitable for producing steam. Food items to be steamed are placed in the steam chamber.
Boilerless steamers currently being manufactured and in use utilize electricity as a source of heat. In these conventional steamers, the steam chamber is heated by electric heating elements disposed beneath the bottom of the steam chamber. The heat transferred to the steam chamber heats the water in the lower portion of the steam chamber, producing steam. One problem with these conventional steamers is the tendency of the steam, when it comes in contact with the walls of the steam chamber, to condense, reducing heat transfer to the product and steamer productivity and negatively impacting product quality. In conventional electrically heated boilerless steamers, this problem is addressed by the use of electric heating tapes positioned around and in contact with the upper portions of the steam chamber. The heating tapes heat the upper portions of the steam chamber, resulting in maintaining wall temperatures slightly above the saturated steam temperature, thereby substantially preventing its condensation. The desirability of using natural gas or some other fossil fuel instead of electricity and of eliminating the use of electric heating tapes from both capital and operating cost perspectives is apparent.
Accordingly, it is one object of this invention to provide a fossil fuel-fired boilerless steamer so as to eliminate the use of electricity for steam generation, thereby increasing the overall thermal efficiency and reducing operating costs of the boilerless steamer compared to conventional boilerless steamers.
It is another object of this invention to provide a boilerless steamer which addresses the problem of steam condensation without employing electric heating tapes, thereby further increasing its thermal efficiency and reducing capital and operating costs.
These and other objects of this invention are addressed by an apparatus comprising at least one outer wall forming a housing, at least one inner wall disposed within the housing and forming a steam chamber having an interior wall surface and an exterior wall surface, whereby an annular space is formed between the exterior wall surface and the at least one outer wall, at least one fossil fuel burner disposed within the housing beneath the bottom of the steam chamber by which products of combustion from the burning of a fossil fuel are generated in the annular space, and exhaust means for exhausting the products of combustion generated by the at least one burner from the annular space. In accordance with one preferred embodiment of this invention, the at least one burner is a gaseous fuel-fired burner.
To produce steam in the boilerless steamer of this invention, water is introduced into a lower portion of the steam chamber and a mixture of a gaseous fuel and an oxidant is burned in a portion of the annular region disposed beneath the bottom of the steam chamber, forming products of combustion and forming steam from the water in the lower portion of the steam chamber. The upper portion of the exterior of the steam chamber is contacted with hot products of combustion, resulting in heating of the walls of the upper portion of the steam chamber, after which the products of combustion are exhausted from the steamer housing through a pipe located above the upper portion of the steam chamber.